Analog and Digital Electronics, Lighting an LED, Building an Amplifier to Boost Current from an Audio Player

Analog and Digital Electronics

A cell phone was connected to a speaker which was all connected to the oscilloscope.  A tone generator app was downloaded on the phone and different tones were shown across the oscilloscope.  The max voltage the phone will put out through an audio jack was found using the oscilloscope and it can be seen that as the frequency increases, the voltage decreases (see whiteboard)

As frequency increases voltage decreases

Max Voltage Produced by Phone

A song was also played on the oscilloscope and the different voltages the music produces is shown across the screen.

Jack Johnson on an Oscilloscope

-adding a capacitor to the circuit with the speaker

Capacitors are frequency dependent so when you add a capacitor to the circuit with the phone and the speaker, the capacitor acts as a low pass filter so it passes low frequencies and blocks or gets rid of high frequencies which are high pitched.

Lighting an LED

A circuit was made with a protoboard, a 150 ohm resistor, and a led light bulb.  The light bulb is a diode so when you put power into the led light backwards, it does not light because you are making the depletion zone bigger.  The led light bulb also needs a minimum amount of voltage to light the bulb because you need that minimum voltage to close the depletion zone.

  A switch was then added to the circuit so you could turn on and off the light bulb.  

lighting LED with switch

Building an Amplifier to Boost Current from an Audio Player

An amplifier was made to make the noise coming from the cell phone louder than the max voltage 

the phone can produce.